The dictionary meaning of nonce word is "a word coined for one single occasion only." In the patent world, nonce words are better understood as generic terms that do not conjure any definite structure on their own. Examples of nonce words used in the patent world are means, module, mechanism, element, and device. Nonce words typically have to be used in combination with an intended effect to conjure structure.
In patent claims, use of means in combination with specification of a function may invoke 35 USC 112(f) (or pre-AIA 35 USC 112, sixth paragraph). Patent drafters tend to use this claiming format when coverage of any manner of achieving a function is desired, but the effect of this claiming format tends to be quite the opposite. For example, the possible structures conjured by "means for sheltering from rain" are numerous. Such means for sheltering may be, for example, a house, a car, or an umbrella, each of which would be under a different class in the patent classification system. Thus, 35 USC 112(f) (or pre-AIA 35 USC 112, sixth paragraph) includes a built-in mechanism for preventing overly broad claims, or even preventing nonsensical claims, by limiting the claim limitation to corresponding structure, material, or acts described in the specification and equivalents thereof.
35 USC 112(f) — An element in a claim for a combination may be expressed as a means or step for performing a specified function without the recital of structure, material, or acts in support thereof, and such claim shall be construed to cover the corresponding structure, material, or acts described in the specification and equivalents thereof.
Since "means" is a clear trigger word under 35 USC 112(f) (or pre-AIA 35 USC 112, sixth paragraph), patent drafters who do not want to invoke 35 USC 112(f) (or pre-AIA 35 USC 112, sixth paragraph) avoid using "means" or "means for" in claim limitations. However, the same patent drafters may attempt to achieve the same effect as means-plus-function by using other nonce words besides means.
The patent in suit in Williamson v. Citrix Online, LLC, 792 F.3d 1343 (Fed. Cir. 2015) used the word "module" in a claim limitation. This limitation reads as follows:
a distributed learning control module for receiving communications transmitted between the presenter and the audience member computer systems and for relaying the communications to an intended receiving computer systems and for coordinating the operation of the streaming data module
The trigger words here are "module," which does not connote sufficiently definite structure by itself, and "for," which signifies the beginning of a specification of a function. In Williamson v. Citrix Online, LLC, the court observed that if the word "module" is replaced with "means," the entire limitation will be consistent with the traditional means-plus-function limitation. The court found that the term "distributed learning control module" is a means-plus-function limitation because (i) module is a nonce word that can be used as a substitute for means, (ii) modifying module with "distributed learning control" does not impart any structural significance to the meaning of module, and (iii) the claim did not describe how the distributed learning control module interacted with other components in the distributed learning control server so that one may infer the structural character of the limitation.
Having determined that the limitation falls under pre-AIA 35 USC 112, sixth paragraph, the specification would need to recite structure corresponding to the term "distributed learning control module" for the claim to be valid. As observed from the excerpt above, the distributed learning control module is required to perform three functions: (1) receive communications transmitted between the presenter and the audience member computer systems, (2) relay the communications to an intended receiving computer systems, and (3) coordinate the operation of the streaming data module. Therefore, the specification would need to describe structure, material, or acts to support these functions. However, the court found that there was no corresponding supporting structure for the term "distributed learning control module" in the specification, rendering the term indefinite and the claim invalid. In particular, the court found that the specification did not disclose an algorithm corresponding to coordinating the operation of the streaming data module.
The court provided some guidance on what would have been corresponding supporting structure. Specifically, the court noted that it is clear from the specification of the patent that the distributed learning control module must be implemented in a special purpose computer that is programmed to perform particular functions. The opinion of the court made it clear that the specification should have disclosed an algorithm for performing the claimed function, which may have been expressed as a mathematical formula, in prose, as a flow chart, or in any other manner that provides sufficient structure.
Williamson v. Citrix Online, LLC highlights a key problem with the U.S. patent system, where there is no guarantee that a patent that is granted by the patent office is valid. In this case, the patent office during prosecution of the patent in suit either failed to properly classify the claim limitation as a means-plus-function limitation or failed to verify that the specification provided sufficient structure for the means-plus-function limitation.